title: Acinetobacter baumannii secretes cytotoxic outer membrane protein A via outer membrane vesicles.
abstract: Acinetobacter baumannii is an important nosocomial pathogen that causes a high morbidity and mortality rate in infected patients, but pathogenic mechanisms of this microorganism regarding the secretion and delivery of virulence factors to host cells have not been characterized. Gram-negative bacteria naturally secrete outer membrane vesicles (OMVs) that play a role in the delivery of virulence factors to host cells. A. baumannii has been shown to secrete OMVs when cultured in vitro, but the role of OMVs in A. baumannii pathogenesis is not well elucidated. In the present study, we evaluated the secretion and delivery of virulence factors of A. baumannii to host cells via the OMVs and assessed the cytotoxic activity of outer membrane protein A (AbOmpA) packaged in the OMVs. A. baumannii ATCC 19606(T) secreted OMVs during in vivo infection as well as in vitro cultures. Potential virulence factors, including AbOmpA and tissue-degrading enzymes, were associated with A. baumannii OMVs. A. baumannii OMVs interacted with lipid rafts in the plasma membranes and then delivered virulence factors to host cells. The OMVs from A. baumannii ATCC 19606(T) induced apoptosis of host cells, whereas this effect was not detected in the OMVs from the ΔompA mutant, thereby reflecting AbOmpA-dependent host cell death. The N-terminal region of AbOmpA(22-170) was responsible for host cell death. In conclusion, the OMV-mediated delivery of virulence factors to host cells may well contribute to pathogenesis during A. baumannii infection.
authors.affiliation: Department of Microbiology, Kyungpook National University School of Medicine, Daegu, Korea.
authors.forename: Jong Sook
authors.initials: JS
authors.lastname: Jin
authors.forename: Sang-Oh
authors.initials: SO
authors.lastname: Kwon
authors.forename: Dong Chan
authors.initials: DC
authors.lastname: Moon
authors.forename: Mamata
authors.initials: M
authors.lastname: Gurung
authors.forename: Jung Hwa
authors.initials: JH
authors.lastname: Lee
authors.forename: Seung Il
authors.initials: SI
authors.lastname: Kim
authors.forename: Je Chul
authors.initials: JC
authors.lastname: Lee
mesh_terms: D000151:Acinetobacter Infections / Q000378:metabolism / Q000382:microbiology / Q000473:pathology; D040981:Acinetobacter baumannii / Q000378:metabolism* / Q000472:pathogenicity / Q000502:physiology / Q000648:ultrastructure; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D006367:HeLa Cells; D054884:Host-Pathogen Interactions / Q000502:physiology; D006801:Humans; D017434:Protein Structure, Tertiary / Q000502:physiology; D022142:Secretory Vesicles / Q000378:metabolism*; D013205:Staphylococcal Protein A / Q000737:chemistry / Q000378:metabolism*; D020298:U937 Cells; D037521:Virulence Factors / Q000737:chemistry / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; D013205:Staphylococcal Protein A; D037521:Virulence Factors